1. Field of Invention
This invention relates to record material. It more particularly relates to such record material in the form of sheets or rolls coated with color-forming systems comprising chromogenic material (electron-donating dye precursors) and acidic color developer material. This invention particularly concerns record material capable of forming non-reversible images and capable of being desensitized.
2. Description of Related Art
Thermally-responsive record material systems are well known in the art and are described in many patents, for example, U.S. Pat. Nos. 3,539,375; 3,674,535; 3,746,675; 4,151,748; 4,181,771; 4,246,318; and 4,470,057 which are incorporated herein by reference. In these systems, basic chromogenic material and acidic color developer material are contained in a coating on a substrate which, when heated to a suitable temperature, melts or softens to permit said materials to react, thereby producing a colored mark.
Thermally-responsive record materials have characteristic thermal responses, desirably producing a colored image of sufficient intensity upon selective thermal exposure. Improvements in thermal response would be of commercial significance.
A drawback of conventional thermally-responsive record materials or facsimile paper limiting utilization in certain environments and applications has been the undesirable tendency of thermally-responsive record materials upon forming an image to not retain that image in its original integrity over time when the thermally-responsive record material is subsequently handled. The thermally-sensitive coating of a thermally-responsive record material continues to be active after imaging. For example, facsimile papers, even after imaging, if scratched by a blunt instrument or if exposed to temperatures above about 50.degree. C.-55.degree. C. will blacken, respectively. As a result, due care and control in handling imaged thermally-responsive record materials has been required.
U.S. Pat. No. 4,529,681 discloses a light- and heat-sensitive record material relying on use of permeable capsules relying on heat to effect coloring component permeation through the thermoplastic capsule wall.
The ability of a thermally-responsive record material to be able to be resistant to ambient heating appears contradictory. However, it is an object of the present invention to disclose a novel record material bearing non-meltable capsules resistant to ambient heat but said capsules capable of rupture in a thermal printer and said record material capable of being deactivated after imaging.